aria-ambient attribute for images?

In reviewing this article from CanAdapt
<http://davidmacd.com/blog/what-is-pure-decoration-alt-text-in-wcag.html>
on purely decorative versus ambient images, an idea occurred to me. It seems
like it would be useful for the next iteration of ARIA to include an
"aria-ambient" attribute for images.  That way screen reader users could
configure a default behavior for their assistive technologies and users who
find ambient images valuable could have them read, while others could
ignore them.  As it stands now, screen reader users who don't want to hear
this extra noise have to listen to at least part of the alternative text to
know whether it can safely be skipped, no?  Has the Aria Working Group
considered the issue from this angle?

-- 
Rob Fentress
Senior Accessibility Solutions Designer
Assistive Technologies at Virginia Tech
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